Sodium Binding Interactions with Aliphatic Amino Acids: A Guided Ion Beam and Computational Study
Hanh D M Pham1, Georgia C Boles1, P B Armentrout1
1Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, United States.
The Journal of Physical Chemistry. A
|July 16, 2021
Summary
Sodium cation (Na+) binding affinities with six aliphatic amino acids were measured. Bond dissociation energies increase with amino acid polarizability, offering insights into protein stability and metal interactions.
Area of Science:
- Biophysical Chemistry
- Chemical Physics
- Biochemistry
Background:
- Metal binding affinities are crucial in various scientific and industrial fields.
- Amino acid interactions with metal cations significantly influence protein structure and stability.
- Understanding these interactions is key to advancing medicinal and biological applications.
Purpose of the Study:
- To comprehensively investigate the interactions between sodium cations (Na+) and six aliphatic amino acids: glycine, alanine, homoalanine, valine, leucine, and isoleucine.
- To determine the absolute bond dissociation energies (BDEs) for these Na+-amino acid complexes.
- To correlate structural and energetic properties with amino acid polarizability.
Main Methods:
- Utilized threshold collision-induced dissociation (CID) in a guided ion beam tandem mass spectrometer to study Na+-amino acid interactions.
- Analyzed kinetic-energy-dependent dissociation cross sections, accounting for experimental variables.
- Performed quantum chemical calculations using multiple levels of theory (B3LYP, B3P86, MP2, B3LYP-GD3BJ, M06-2X) for comparison.
Main Results:
- Determined absolute BDEs for Na+-amino acid complexes: Gly (164.0), Ala (166.9), hAla (167.9), Val (172.7), Leu (173.7), and Ile (174.6) kJ/mol.
- Experimental BDEs showed favorable agreement with theoretical calculations across various computational methods.
- Observed a clear linear correlation between increasing BDEs and increasing amino acid polarizability.
Conclusions:
- The study provides precise BDEs for Na+-aliphatic amino acid interactions.
- Amino acid polarizability is identified as a primary factor governing the strength of Na+ binding.
- Findings contribute to a deeper understanding of cation-amino acid interactions relevant to protein stability and biomolecular recognition.
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